Non-return valves are in particular used in exhaust gas return lines to prevent air from flowing from the charge air line into the exhaust gas return line when the pressure in the charge air line is higher than the pressure in the exhaust gas return line due to pressure variations in the exhaust gas region. These valves are adapted to open and close as quickly as possible so that, in most cases, they are designed as flutter valves which include spring leaf elements which serve as valve closing members. Since the opening cross section of such flutter valves is limited and opening limiters in the form of stopper elements are to be provided to prevent the leaf springs from breaking, these valves are in most cases configured as multi-pass valves. Since return flows within the exhaust gas return duct are prevented by these non-return valves, the exhaust gas return rate is increased when these valves are used, which, in turn, results in a reduction of pollutants.
DE 10 2009 007 609 A1 describes a multi-pass non-return valve where the stopper elements and the valve closing members are integrally configured and inserted and/or pushed into respective holders of the housing. The flow cross sections are respectively arranged in pairs located opposite to each other.
EP 1 098 085 A2 describes a four-pass non-return valve which comprises a valve housing made up of two elements arranged like prisms relative to each other whose side faces respectively form two valve seats which define flow apertures. Each valve seat is associated with a leaf spring element acting as a closing body and a stopper element. The valve housing comprises clamping faces where the leaf springs and the stopper elements are fastened by means of screws.
CN 201 739 030 U describes a non-return valve disposed in a duct housing which is made up of two prism-shaped valve housings arranged side by side. The surrounding housing comprises a reduced portion along the valve housings to reduce the cross section of the duct housing to the cross section of a downstream throttle flap.
DE 20 2005 019 518 U1 and JP 59-155673 A describe exhaust gas non-return valves where the leaf springs, in their fully open state, extend to a location close to the surrounding housing which, in accordance with DE 20 2005 019 518 U1, comprises a reduced portion adjacent to the non-return valve.
All of the above-described non-return valve devices are disadvantageous in that return flows and swirls are produced due to the occurring pulsations in the region next to the leaf spring elements, i.e., between the leaf spring elements and the surrounding housing, or, if the leaf spring elements face each other, between them. These backward swirls increase the pressure loss and accordingly reduce the pressure gradient required for an exhaust gas return flow, which results in a reduced efficiency of the internal combustion engine.